The invention relates to a compressed air supply system for a commercial vehicle having a compressed air inlet that can be coupled to a compressor, a filter module coupled to the compressed air inlet via a delivery line, a discharge valve coupled to a discharge outlet and the delivery line, an energy-saving control outlet that can be coupled to a control inlet of the compressor, and a first valve unit together with a second valve unit, the valve units serving to control the discharge valve, the energy-saving control outlet and the regeneration of the filter module.
The invention further relates to a method for operating a compressed air supply system having a compressed air inlet that can be coupled to a compressor, a filter module coupled to the compressed air inlet via a delivery line, a discharge valve coupled to a discharge outlet and the delivery line, an energy-saving control outlet that can be coupled to a control inlet of the compressor, and a first valve unit together with a second valve unit, the valve units serving to control the discharge valve, the energy-saving control outlet and the regeneration of the filter module.
Such compressed air supply systems fulfill numerous functions in commercial vehicles. These include, in particular, the supply of dry, purified compressed air to the braking system and other compressed air consumers, the exercise of a multi-circuit safety valve function to safeguard various consumer circuits and to ensure a specific filling order and the provision of a pressure regulator function. The compressed air used by the compressed air consumers is provided primarily by a compressor, which is generally driven by the internal combustion engine of the commercial vehicle. In many systems the compressor can be brought into an energy-saving state, either by separating a clutch, which serves to couple the compressor to the internal combustion engine, or by pneumatic actuation of a compressor control inlet, in order to bring the compressor into an idling state. Such energy-saving measures may be further supported in that the operating sequences in the compressed air supply system, as far as possible, take place in such a way that compressed air, once generated, does not needlessly go to waste.
It should be noted here that a certain compressed air loss is unavoidable, since the filter module of the compressed air supply system has to be repeatedly regenerated. For this purpose, dry compressed air is fed from the compressed air reservoirs connected to the compressed air supply system through the filter module in a direction opposed to the delivery direction. The air flowing through the filter module at least partially absorbs the moisture in the filter unit before flowing out into the open via the discharge valve of the compressed air supply system.
EP 1 318 936 B1 describes a compressed air supply system, which is equipped with a regeneration function and an energy-saving outlet for bringing a compressor into an idling state. Provision is made for two solenoid valves, which perform these functions. The intention here is to link the opening of the regeneration air path to the opening of the discharge valve. In this way the compressed air is lost from the volume between the discharge valve and a non-return valve, arranged downstream of the filter module and facing the consumers, only when this is unavoidable due to the regeneration required.
In other systems in the state of the art, the energy-saving state is linked to the opening of the discharge valve, that is to say whenever the compressor is brought into an energy-saving state the discharge valve is also opened. In the absence of any countermeasures, this results in an unnecessary pressure loss over the entire delivery line upstream of a non-return valve, which faces the consumers and is arranged downstream of the filter module.
The object of the invention is to provide a compressed air supply system and a method of operation affording a high potential energy saving and an increase in the functionality compared to the state of the art.
This object is achieved by a compressed air supply system for a commercial vehicle having a compressed air inlet that can be coupled to a compressor, a filter module coupled to the compressed air inlet via a delivery line, a discharge valve unit coupled to a discharge outlet and the delivery line, an energy-saving control outlet that can be coupled to a control inlet of the compressor, and a first valve unit together with a second valve unit. The valve units serve to control the discharge valve unit, the energy-saving control outlet and the regeneration of the filter module. The first valve unit serves to control a first control inlet of the discharge valve unit, the energy-saving control outlet and the regeneration of the filter module. The second valve unit serves to control a second control inlet of the discharge valve unit.
Advantageous embodiments of the invention are described herein.
The invention is based on a compressed air supply system, in which the first valve unit serves to control a first control inlet of the discharge valve unit, the energy-saving control outlet and the regeneration of the filter module, and the second valve unit serves to control a second control inlet of the discharge valve unit. The compressed air supply system can therefore be regenerated solely by switching over the first valve unit, since both the regeneration air path and the discharge valve can be opened by switching over the first valve unit. At the same time by switching over the first valve unit the compressor connected to the energy-saving control outlet is switched over into an idling state or an operating state with reduced energy consumption. In order to be able to bring about this idling state of the compressor even when regeneration is not desired or necessary, however, the discharge valve unit has a second control inlet, which can be actuated by the second valve unit. The discharge valve can thereby be kept closed even when the first control inlet of the discharge valve is being ventilated.
The first valve unit usefully evacuates the first control inlet of the discharge valve unit in a first switching state and ventilates the first control inlet of the discharge valve unit in a second switching state, and the discharge valve unit is brought into an opened state by ventilation of the first control inlet when the second control inlet is evacuated. If neither the first nor the second control inlet of the discharge valve is ventilated, the second control inlet is closed. If the second control inlet remains evacuated, whilst the first control inlet is ventilated, the discharge valve can be opened.
In particular, the second valve unit evacuates the second control inlet of the discharge valve unit in a first switching state and ventilates the second control inlet of the discharge valve unit in a second switching state, and the discharge valve unit is closed when the second control inlet is ventilated, even when the first control inlet is ventilated. This means that the second control inlet of the discharge valve has priority over the first control inlet. If the same pressures prevail on both control inlets, the ventilation of the first control inlet has no effect. This can be achieved in that the force developed by the ventilation of the second control inlet is assisted by a spring or in that the control inlets have different effective pressure areas so that, given identical pressures, different forces act on a control element of the discharge valve.
Providing two valve units, each having two switching states, means that in total four possible operating states are available, whereby in a first operating state of the compressed air supply system the first valve unit assumes its first switching state and the second valve unit assumes its first switching state, so that a first delivery operating state prevails. The regeneration air path is closed, the compressor is in its delivery phase and the discharge valve is closed.
Furthermore, in a second operating state of the compressed air supply system, the first valve unit assumes its first switching state and the second valve unit assumes its second switching state, so that a second delivery operating state prevails. The regeneration air path is closed, the compressor is in its delivery phase and the discharge valve is closed. In contrast to the first delivery operating state, in the second delivery operating state, the second control inlet, which was evacuated in the first delivery operating state, is ventilated. This does not lead to a change in the switching state of the discharge valve unit, since the discharge valve unit assumes its closed state even when the control inlets are evacuated.
Furthermore, in a third operating state of the compressed air supply system, the first valve unit assumes its second switching state and the second valve unit assumes its first switching state, so that a regeneration operating state prevails. The regeneration air path is opened, the discharge valve is opened and the compressor is in its idling phase.
Furthermore, in a fourth operating state of the compressed air supply system, the first valve unit assumes its second switching state and the second valve unit assumes its second switching state, so that a closed operating state prevails. Irrespective of whether the regeneration air path is opened or closed in the fourth operating state, the discharge valve is in any case in its closed state due to the ventilated second control inlet. Consequently any outflow of compressed air from the system through the discharge valve is blocked, that is to say, in particular, even when the regeneration air path is opened.
According to a preferred embodiment of the present invention, the first valve unit is arranged in a regeneration air path of the compressed air supply system. The first valve unit is therefore part of the regeneration air path. If in this case, both the first valve unit and the second valve unit are in their second switching state, an outflow of compressed air will be prevented solely because the discharge valve is kept closed by ventilation of the second control inlet.
A regeneration valve unit, which can be actuated via the first valve unit, may likewise be provided, the regeneration valve unit being arranged in a regeneration air path of the compressed air supply system. Such a regeneration valve unit may afford a favorable solution in terms of an adequate rate of flow of regeneration air. The presence of the regeneration valve unit may furthermore provide an extended switching circuit logic.
In this context, in particular, the regeneration valve unit may have a first control inlet, via which it can be pneumatically actuated by the first valve unit, and the regeneration valve unit may have a second control inlet, via which it can be pneumatically actuated by the second valve unit.
The second valve unit then evacuates the second control inlet of the regeneration valve unit in its first switching state and ventilates the second control inlet of the regeneration valve unit in its second switching state, and the regeneration valve unit is closed when the second control inlet is ventilated, even when the first control inlet is ventilated. That is to say if the two actuating valve units in such a regeneration valve unit incorporated into the circuit are both in their second switching state, both the discharge valve unit and the regeneration valve unit are closed.
In an especially preferred development of the invention, the second valve unit is coupled to a control line, which serves to perform further control functions in the compressed air supply system. Since most aspects of the functionality in terms of switching between the delivery operating state and the regeneration operating state are achieved in that the first valve unit switches whilst the second valve unit only has to keep the discharge valve closed in respect of the closing function when the compressor is idling, further functions, in particular further control functions of the compressed air supply system, can be assigned to the second valve unit.
For example, the control line may be connected to a control inlet of an overflow valve supplying a consumer circuit. The overflow valves, which supply the consumer circuits, are coordinated in respect of their opening and closing pressures in such a way that the individual consumer circuits are reciprocally safeguarded and that a predefined filling order is adhered to. Since the overflow valves are equipped with a control inlet, which is connected to the control line leading to the second valve unit, this makes it possible to influence the functions of the overflow valves that can be actuated in this way.
For example, by ventilating the control inlet it is possible to assist opening of the overflow valve. A consumer circuit of intrinsically low filling priority can thereby purposely be given filling preference. This may relate, in particular, to the compressed air circuit assigned to the pneumatic suspension system of the vehicle or to other circuits that can be filled without sacrificing safety in a state of the commercial vehicle, in which a sufficient braking action cannot yet be achieved. It is likewise possible to keep the overflow valves connected to the control line permanently open, so that closing is prevented when the pressure falls below the closing pressure.
According to another aspect, ventilation of the control inlet may serve to bring about and maintain a closed state of the overflow valve. This makes it possible, in particular, to separate a defective circuit from the other circuits, so that the compressed air system can continue to be operated in its optimum operating pressure range without losing compressed air via the defective circuit.
The valve units are usefully 3/2-way valves. This provides the connections and switching states required for the functions described.
An electronic control module may, in particular, be provided and the valve units may be solenoid valves. In this way, the various operating states of the compressed air supply system can be assumed on the basis of intelligent calculations, making it possible, in particular, to take a lot of data relating to the commercial vehicle into account. This data can be supplied directly to the electronic control module or via a data bus, it being possible to connect various other control modules of the commercial vehicle to a data bus, so as to exchange data with the control module of the compressed air supply system.
The discharge valve unit may furthermore be a 2/2-way valve. It is also useful for the regeneration valve unit to be a 2/2-way valve.
Since the functions of the discharge valve unit and the regeneration valve unit are linked by virtue of the parallel pressurization of their control inlets, according to a further embodiment, the discharge valve unit and the regeneration valve unit are integrated into a 4/2-way valve. Two connections of the 4/2-way valve serve for discharging compressed air, whilst the remaining connections are provided for the regeneration air path.
The method of operating the compressed air supply system has the first valve unit serving to control a first control inlet of the discharge valve unit, the energy-saving control outlet and the regeneration of the filter module, and the second valve unit serving to control a second control inlet of the discharge valve unit. In this way, the advantages and particular features of the compressed air supply system according to the invention are also embodied as a method. This also applies to the especially preferred embodiments of the method according to the invention specified below.
In a useful development of the method, the first valve unit evacuates the first control inlet of the discharge valve unit in a first switching state and ventilates the first control inlet of the discharge valve unit in a second switching state, and the discharge valve unit is brought into an opened state by ventilation of the first control inlet when the second control inlet is evacuated.
The second valve unit furthermore evacuates the second control inlet of the discharge valve unit in a first switching state and ventilates the second control inlet of the discharge valve unit in a second switching state, and the discharge valve unit is closed when the second control inlet is ventilated, even when the first control inlet is ventilated.
In an especially preferred embodiment of the invention, in a first operating state of the compressed air supply system, the first valve unit assumes its first switching state and the second valve unit assumes its first switching state, so that a first delivery operating state prevails.
Furthermore, in a second operating state of the compressed air supply system, the first valve unit assumes its first switching state and the second valve unit assumes its second switching state, so that a second delivery operating state prevails.
In a third operating state of the compressed air supply system, the first valve unit preferably assumes its second switching state and the second valve unit assumes its first switching state, so that a regeneration operating state prevails.
Furthermore, in a fourth operating state of the compressed air supply system, the first valve unit usefully assumes its second switching state and the second valve unit assumes its second switching state, so that a closed operating state prevails.
In one embodiment of the method according to the invention, the first valve unit is arranged in a regeneration air path of the compressed air supply system. A regeneration valve unit may likewise be actuated via the first valve unit, the regeneration valve unit being arranged in a regeneration air path of the compressed air supply system. In this case, the regeneration valve unit usefully has a first control inlet, via which it is pneumatically actuated by the first valve unit, and the regeneration valve unit has a second control inlet, via which it can be pneumatically actuated by the second valve unit.
In particular, the second valve unit evacuates the second control inlet of the regeneration valve unit in its first switching state and ventilates the second control inlet of the regeneration valve unit in its second switching state, and the regeneration valve unit is closed when the second control inlet is ventilated, even when the first control inlet is ventilated.
In an especially preferred embodiment of the present invention, the second valve unit is coupled to a control line, which serves to perform further control functions in the compressed air supply system. In this context it is particularly advantageous if the control line is connected to a control inlet of an overflow valve supplying a consumer circuit. According to one variant, opening of the overflow valve is assisted by ventilation of the control inlet.
In another method according to the invention, ventilation of the control inlet serves to bring about and maintain a closed state of the overflow valve. The valve units are usefully actuated by an electronic control module.
The invention is based on the finding that an unnecessary energy consumption due to the loss of compressed air can be avoided or prevented by an intelligent configuration of the regeneration and discharge system of the compressed air supply system. Here, the compressed air is retained in the system whenever possible. The outflow of compressed air is limited to periods when an outflow is unavoidable due to a necessary or desired regeneration of the filter module. The solution according to the invention provides independent control of the discharge valve unit and the energy-saving unit of the compressor, even though switching between the delivery phase and the regeneration phase can be brought about by the switching of a single valve unit. The discharge valve is opened only during the regeneration or in special flushing phases aimed at preventing a compressed air line from freezing up. The same valve unit as is used, at least in some embodiments of the present invention, for switching between the regeneration phase and the closed operating state may also serve to ensure an ongoing control of the compressed air supply system. In this case, a separate control inlet allows overflow valves to be controllably opened or kept open independently of their opening and closing pressures. Overflow valves can likewise be controllably closed or kept closed so as to permit the preferred filling of circuits which are connected to other overflow valves. In particular, this makes it possible, by closing the associated overflow valve and therefore isolating the defective circuit, to prevent any adverse effect on the compressed air supply system due to a circuit defect. Such a control over the sequences in the various consumer circuits can be performed on the basis of pressure data. In this case useful feedback and control concepts can be implemented via the control module, the compressed air supply system and other systems arranged in the vehicle.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.